import java.util.Stack;

class MyQueue {
    private Stack <Integer> s1;
    private Stack <Integer> s2;
    public MyQueue() {
        this.s1 = new Stack<>();
        this.s2 = new Stack<>();
    }

    public void push(int x) {
        s1.push(x);
    }

    public int pop() {
        if(empty()){
            return -1;
        }
        if (s2.empty()){
            while (!s1.empty()){
                s2.push(s1.pop()) ;
            }
        }
        return  s2.pop();
    }

    public int peek() {
        if(empty()){
            return -1;
        }
        if (s2.empty()){
            while (!s1.empty()){
                s2.push(s1.pop()) ;
            }
        }
        return  s2.peek();
    }

    public boolean empty() {
        return s1.empty()&&s2.empty();
    }
}

/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue obj = new MyQueue();
 * obj.push(x);
 * int param_2 = obj.pop();
 * int param_3 = obj.peek();
 * boolean param_4 = obj.empty();
 */